Originally, power line networking was conceived for the networking and high-speed transport of data in small office and home office environments. Recently, a specification entitled “HomePlug 1.0 Specification,” was published by the HomePlug Network Alliance. The HomePlug 1.0 Specification provides functions, operations and interface characteristics for high-speed networking based on Orthogonal Frequency Division Multiplexing (OFDM) modulation and using power line wiring as its medium.
The HomePlug 1.0 Specification identifies four modes of operation, all supporting high-rate data transmissions over a power line. These modes of operation include a Robust (ROBO) mode, a Differential Binary Phase Shift Keying (DBPSK) mode and two different speeds of Differential Quadrature Phase Shift Keying (“¼” DQPSK and “¾” DQPSK). For instance, the ROBO mode is a robust form of Differential Binary Phase Shift Keying (DBPSK) that provides extensive time and frequency diversity to improve performance of a system under adverse conditions.
The maximum possible PHY layer payload transmission rate supported by these modes of operation normally ranges from one megabits per second (Mbps) for ROBO mode to 13 megabits per second (Mbps) for DQPSK (¾). These rates are realized by employing an extensive digital signal processor (DSP) computational power at the transmitter and receiver. It is now being realized that the current HomePlug standard fails to provide a low-cost solution to support stations operating at substantially lower data rates such as automation control devices (e.g., home appliances, security and monitoring devices and light/temperature scheduling devices).
The development of a mode of operation that supports low-rate data transmissions without altering operations supported by the current HomePlug standard may be useful for a variety of applications. Also, such development would provide substantial cost savings to allow manufacturers to produce different cost and complexity levels of HomePlug compliant stations.